40 Dr Andrew Fyfe on (he Comparative Value of 



sp. gv. from 460 to 520. The quantity of gas from a ton of 

 coal was 9500 feet.* 



Newcastle coal-gas being by the chlorine 4"33, and the 

 Wigan cannel gas, 7'55, they are as 1 to 1-73. The dura- 

 bility being 50' 30" and 57', they are 1 to 1'12. Taking both in- 

 to account, then the value is as 1 to 1-93 (1 : 1-73 : : 1'12 : 1-93), 

 which is nearly the same as that of the gas from Yorkshire 

 cannel, already given as ISl. We may take the avei'age 

 value of the gas from English parrot coal, so far as these 

 trials go, as 1'85 compared to that from English caking coal, 

 as 1. 



Scottish Parrot Coat. — I have had many opportunities of 

 testing the quality of gas from this kind of coal, not only as 

 manufactured at gas-works, but also when made by my ex- 

 perimental apparatus in Edinburgh and Aberdeen. I have, 

 already in a paper, published in the Transactions of the So- 

 ciety, for 1842, given the results of numerous trials conduct- 

 ed in Edinburgh. I have now to allude, not only to those 

 made in different towns of Scotland, but also to a very ex- 

 tended series, more lately carried on with the experimental 

 apparatus. 



The gas, from all the varieties of Scottish parrot coal, is 

 of superior quality to that from the best English parrot ; 

 but it varies very much according to the kind of coal. In all 

 of the towns in Scotland that I have visited, a mixture of one 

 of fine quality, and of one or more of inferior quality, is em- 

 ployed in the manufacture of gas ; partly, because the former 

 cannot be got in sufficient quantity ; partly, because it is 

 too expensive ; and hence, with one or two exceptions, chiefly 

 in the smaller towns, the quality of the gas was found to be 

 very nearly the same. 



In the paper already alluded to, I have stated the conden- 

 sation by chlorino, with the gases prepared from the coals 

 there mentioned, to vary from 9 to about 20. With two ex- 

 ceptions, I never found it under 12 ; the average of all the 



* In one instance I found the quantity of gas amount to 11,500 feet ; but in 

 this case the quality of the gas was not so good. I prefer, therefore, taking 

 the one above. 



